The only one that I've found in my travels is MCN (Macon, GA), which has already been mentioned.

Starting June 7, Delta will start serving SLE (Salem, Oregon), and it will be the only carrier at least for a while. SkyWest will serve the airport for Delta Connection with two flights per day to and from SLC.

Commercial flights ended from SLE in 1993 as too many passengers went to nearby PDX and EUG (mainly PDX). I remember occasionally flying out of SLE as a child. But not often, we usually went to PDX since it was closer.

I may get the chance to try out the new service in late June.

I wouldn't be too surprised to see other carriers follow if Delta has success. Particulary Horizon Air (Alaska), which services a lot of smaller airports in Oregon.